Normally, a woman’s menstruation is dark red and does not clot, so the menstrual blood is clot-free. If menstruation appears bright red, the following causes are common in clinical practice: a. Submucosal fibroids cause the endometrial area to increase, which affects the contraction of the uterus, so the menstrual blood is bright red and the volume is relatively high, and the duration of menstruation is also prolonged. Second, due to endometrial lesions, such as endometrial cancer, or endometrial inflammation, or other causes of endometrial lesions, bright red menstrual color may also occur. Third, clinically caused by coagulation dysfunction, such as thrombocytopenia, or other blood disorders, can also cause changes in the color of menstruation, so this situation is recommended to do routine blood tests and ultrasound to understand the specific situation before giving treatment.